Ethnic Russian Yegor Shcherbakov, 25, was killed on Thursday in front of his girlfriend.

Police have released a security camera photo of the suspect, but have not identified him.

Media said the image suggested the man was of "non-Slavic appearance", leading nationalists to conclude the killer was a Muslim migrant from the Russian North Caucasus.

The issue of immigration and internal migration was one of the main concerns of Muscovites in the recent election of Moscow Mayor Sergei Sobyanin.

Mr Sobyanin ordered Mr Shcherbakov's murder to be thoroughly investigated, but also condemned the rioting and called for those responsible to be held accountable.

The scenes were reminiscent of similar violence in December 2010, when football fans and ultra-nationalists went on the rampage near the Kremlin after the killing of a football fan in a brawl with migrants.